This invention relates to electrolytic capacitors and more particularly, to the mounting of electrolytic capacitors on a base plate, chassis or circuit board.
An electrolytic capacitor generally comprises a cylindrical metallic enclosure containing a plurality of capacitor elements or foils immersed in an electrolyte. Most electrolytic capacitors are provided with a pair of positive and negative electrodes or terminals projecting from one thereof. These electrodes usually have threaded portions for facilitating the attachment of electrical leads thereto. Such capacitors are larger in size and heavier in weight than most of the other electrical circuit components which may be mounted on a chassis or circuit board. The electrolytic capacitor, therefore, must be firmly mechanically mounted on the chassis or circuit board.
While most electrolytic capacitors are sufficiently sealed to contain the electrolyte therein, leakage of the electrolyte can and often does develop after the capacitor has been mounted on the circuit board. The electrolyte is usually a relatively harsh reacting chemical agent which will damage not only the chassis or circuit board but other electrical components with which it may come into contact.
U.S. Pat. No. 4,324,329 discloses a mounting member for an electrolytic capacitor. The mount disclosed in this patent is a cylinder molded from an elastic synthetic resin that comprises a network or web-like structure of diagonal stripes arranged diagonally with respect to the axis of the cylinder. The base of the cylindrical mount is a relatively thick disc of the resin which is integral with the cylindrical section. The cylindrical mount is secured to the chassis by means of screws which are threaded into a tapped hole in the base portion or are threaded into a nut encased within the base portion. Alternatively, the base portion may be provided with extensions of the resin material to extend through openings in the chassis and which may then be thermally fused in situ to form a widened end portion. Upon insertion of the electrolytic capacitor into the open end of the mount, the mount is subjected to a slight compressive effect because of the relationship of the internal diameter of the mount and the outside diameter of the capacitor. The mount thereby expands and thereby readily receives the capacitor.
U.S. Pat. No. 3,340,603 discloses another technique for mounting an electrolytic capacitor which requires a specially designed support member. At one end the support member is provided with a vertical lug having an opening therein and on the opposite end with horizontally projecting lugs. The electrolytic capacitor is provided at one end with at least one index lug which is inserted into the opening of the vertical lug on the support. A clip-like spring is then passed around the body of the electrolytic capacitor at its other end and engages the horizontally extending lugs at the corresponding end of the support member. It will be appreciated that this technique for mounting an electrolytic capacitor requires a specially constructed support member having the aforementioned lugs.
Still another method for securing an electrolytic capacitor to a circuit board is disclosed in U.S. Pat. No. 4,363,078. Here the capacitor is provided with an anchoring terminal which may be inserted through the circuit board and then bent over to hold the capacitor in place.
Probably the most common of capacitor mounting techniques is the clamp type, as sold by P. R. Mallory and Company, among others. These clamps comprise a cylindrical bracket which is secured to the circuit board by outwardly extending tabs. One side of the bracket is slit and the ends thereof are bent outwardly to permit drawing the bracket ends together by means of a screw or a nut and bolt combination. One end of the capacitor is inserted in the bracket and the aforementioned screw or bolt is tightened so as to compress the bracket around the capacitor cylinder and hold it in place.